The use of copolymers of styrene with n-butylmethacrylate or n-butylacrylate as polymeric binders for toner powders is known (see, for example, U.S. Pat. Nos. 4,312,932; 4,324,851; and 4,601,967) and the use of a magenta pigment in toner particles is disclosed (see the aforementioned '932 and '851 patents).
However, heretofore, it has not been possible to employ such styrene/acrylate copolymers in three-color imaging because a suitable magenta colorant for use with such copolymers was not known.
Magenta dyes that are suitable for use with toner powder polyester resins tend to aggregate in styrene/butyl acrylate copolymers. Also, magenta dyes which are lightfast in polyesters are often fugitive in such styrene/butylacrylate copolymers.
It was discovered that 1,4-diamino-2,3-diphenoxy-anthraquinone, a known magenta dye identified as Disperse Violet 31, C.I. 60205, and available commercially from American Hoescht under the designation "Solvaperm.TM. Red Violet R", was dissolvable in such copolymers without aggregation and was lightfast when in such copolymers. However, unfortunately, this dye sublimes from a matrix of such polymer when a toner powder thereof is heat fused.
So far as now known, a suitable magenta dye for compounding with such styrene/butylacrylate copolymer was not known prior to the present invention.